<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <style type="text/css">
        * {
            margin: 0;
            padding: 0;
            width: 100%;
            height: 100%;
        }

        #root {
            width: 1000px;
            display: flex; /* 采用flex布局*/
            flex-wrap: wrap; /* flex布局换行*/
        }

        #head {
            height: 100px;
        }

        #middle {
            display: flex; /* 采用flex布局*/
        }

        #foot {
            height: 100px;
        }

        #left {
            width: 300px;
        }

        #right {
            width: 700px;
        }
    </style>
</head>
<body>
<div id="root">
    <div id="head"></div> <!--head end-->
    <div id="middle">
        <div id="left"></div> <!--left end-->
        <div id="right"></div> <!--right end-->
    </div> <!--middle end-->
    <div id="foot"></div> <!--foot end-->
</div> <!--root-end-->
</body>
</html>